Method of manufacturing an all solid state battery

ABSTRACT

A method of manufacturing an all solid state battery is disclosed. In one embodiment, the method includes forming a negative electrode including a negative active material layer and a negative buffer layer, forming a sulfide-based solid electrolyte layer on a first surface of the negative electrode, forming a positive electrode including a positive active material layer and a positive buffer layer, and bonding the positive electrode to a second surface of the solid electrolyte layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Application No. 17/397,190,filed on Aug. 9, 2021, which claims the benefit of Korean PatentApplication No. 10-2020-0179849, filed in the Korean IntellectualProperty Office on Dec. 21, 2020, which applications are herebyincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an all solid state battery and amanufacturing method thereof.

BACKGROUND

In general, a lithium ion battery using a liquid electrolyte has astructure in which a negative electrode and a positive electrode arepartitioned by a separator, and thus when the separator is damaged bydeformation or external impact, a short circuit may occur, which maylead to a danger such as overheating or explosion.

Accordingly, development of a solid electrolyte capable of securingsafety is a very important task in the field of secondary batteries.

The all solid state battery using the solid electrolyte is advantageousin that safety of the battery may be increased and leakage of anelectrolyte solution may be prevented, so that reliability of thebattery may be improved, and at the same time, it may be easy tomanufacture a thin-type battery.

In addition, lithium metal can be used as the negative electrode, whichcan improve energy density, and accordingly, it is expected to beapplied to high-capacity secondary batteries for electric vehicles aswell as small secondary batteries, and is in the spotlight as anext-generation battery.

In the above-described all solid state battery in the prior art, aplurality of layers are stacked and then bonded through a rollingprocess.

For example, in the all solid state battery according to the prior art,a negative electrode and a positive electrode are symmetrically stackedwith a solid electrolyte therebetween.

In this case, each of the negative electrode and the positive electrodeincludes a hard current collector and a soft active material layer.

Such an all solid state battery may reduce internal porosity by therolling process, but when a material is spring-backed or when chargingor discharging is performed, there is a problem in that voids arere-formed due to a change in a volume of an active material.

In other words, an upper portion of each electrode may act as a bufferduring charging and discharging due to the soft solid electrolyte layerto minimize a change in porosity, but since a lower portion of eachelectrode is formed by adhesion between the hard current collector andthe material, the porosity may increase depending on a volume change atan interface of each material.

Accordingly, in the all solid state battery according to the prior art,ionic conductivity and electronic conductivity may decrease due to anincrease in porosity, and in the long term, this may adversely affectperformance of the battery.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention, andtherefore it may contain information that does not form the prior artthat is already known to a person of ordinary skill in the art.

SUMMARY

The present invention relates to an all solid state battery and amanufacturing method thereof. Particular embodiments relate to an allsolid state battery and a manufacturing method thereof capable ofreducing porosity.

An embodiment of the present invention provides an all solid statebattery and a manufacturing method thereof capable of minimizingelectrode porosity that may occur after a rolling process by applying anegative electrode buffer layer and a positive electrode buffer layerand maximizing interlayer interfacial adhesion areas.

One or more embodiments of the present invention provide an all solidstate battery including a sulfide-based solid electrolyte layer, anegative electrode configured to include a negative active materiallayer stacked on a first surface of the solid electrolyte layer, and anegative buffer layer stacked on a first surface of the negative activematerial layer, and a positive electrode configured to include apositive active material layer stacked on a second surface of the solidelectrolyte layer, and a positive buffer layer stacked on a secondsurface of the positive active material layer.

In addition, the negative electrode may include a negative currentcollector layer configured to have surface roughness formed on a firstsurface thereof, a negative electrode primer layer disposed on a firstsurface of the negative current collector layer and formed of a mixtureof a carbon-based conductive material and a binder, a negative electrodebuffer layer disposed on a first surface of the negative primer layerand formed of a mixture of a sulfide-based material, a conductivematerial, and a binder, and a negative electrode active material layerdisposed on a first surface of the negative buffer layer and made of amixture of a sulfide-based material, a negative electrode activematerial, a conductive material, and a binder to be in contact with thesolid electrolyte layer.

The negative current collector may include at least one of copper,stainless steel, titanium, iron, and nickel.

In addition, the negative primer layer may be formed by mixing aconductive material and a binder at a ratio of 7:3 to 9.5:0.5.

The negative buffer layer may be formed of a mixture of a sulfide-basedmaterial that is set in a range of 60 wt% or more and 90 wt% or less, aconductive material that is set in the range of 9 wt% or more and 30 wt%or less, and a binder that is set in a range of 1 wt% or more and 10 wt%or less, based on 100 wt% of a total weight.

The negative buffer layer may have softness that is higher than that ofthe negative primer layer.

The negative buffer layer may have the same ionic conductivity andelectronic conductivity as those of the negative active material layer.

The negative active material layer may be formed of a mixture of asulfide-based material in a range of 8 wt% to 30 wt%, a negative activematerial in a range of 60 wt% to 90 wt%, a conductive material in arange of 1 wt% to 10 wt%, and a binder in a range of 1 wt% to 10 wt%,based on 100 wt% of a total weight.

The positive electrode may include a positive current collector layerconfigured to have surface roughness formed on a first surface thereof,a positive electrode primer layer disposed on a first surface of thepositive current collector layer and formed of a mixture of acarbon-based conductive material and a binder, a positive electrodebuffer layer disposed on a first surface of the positive primer layerand formed of a mixture of a sulfide-based material, a conductivematerial, and a binder, and a positive electrode active material layerdisposed on a first surface of the positive buffer layer and made of amixture of a sulfide-based material, a positive electrode activematerial, a conductive material, and a binder, to be in contact with thesolid electrolyte layer.

The positive current collector may include at least one of stainlesssteel, titanium, iron, nickel, aluminum, and chromium.

The positive primer layer may be formed by mixing a conductive materialand a binder at a ratio of 7:3 to 9.5:0.5.

The positive buffer layer may be formed of a mixture of a sulfide-basedmaterial that is set in a range of 60 wt% or more and 90 wt% or less, aconductive material that is set in the range of 9 wt% or more and 30 wt%or less, and a binder that is set in a range of 1 wt% or more and 10 wt%or less, based on 100 wt% of a total weight.

The positive buffer layer may have softness that is higher than that ofthe positive primer layer.

The positive buffer layer may have the same ionic conductivity andelectronic conductivity as those of the positive active material layer.

The positive active material layer may be formed of a mixture of asulfide-based material in a range of 8 wt% to 30 wt%, a positive activematerial in a range of 60 wt% to 90 wt%, a conductive material in arange of 1 wt% to 10 wt%, and a binder in a range of 1 wt% to 10 wt%,based on 100 wt% of a total weight.

In accordance with the all solid state battery and a manufacturingmethod thereof according to the embodiments of the present invention, itis possible to minimize electrode porosity that may occur after arolling process by applying a negative electrode buffer layer and apositive electrode buffer layer and maximizing interlayer interfacialadhesion areas.

In addition, in accordance with the all solid state battery and amanufacturing method thereof according to the embodiments of the presentinvention, it is possible to minimize deformation caused by volumechange of the negative active material or positive active material thatmay occur during charging and discharging, resultantly improving a lifecharacteristic.

Further, effects that can be obtained or expected from embodiments ofthe present invention are directly or suggestively described in thefollowing detailed description. That is, various effects expected fromembodiments of the present invention will be described in the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view showing a cross-sectional structureof an all solid state battery according to an embodiment of the presentinvention.

FIG. 2 schematically illustrates a cross-sectional structure of anegative electrode of an all solid state battery according to anembodiment of the present invention.

FIG. 3 schematically illustrates a cross-sectional structure of apositive electrode of an all solid state battery according to anembodiment of the present invention.

FIG. 4 to FIG. 11 illustrate views sequentially showing a manufacturingmethod of an all solid state battery according to an embodiment of thepresent invention.

The following elements may be used in connection with the drawings todescribe embodiments of the present invention.

1 all solid state battery 10 solid electrolyte layer 20 negativeelectrode 21 negative current collector 23 negative primer layer 25negative buffer layer 27 negative active material layer 30 positiveelectrode 31 positive current collector 33 positive primer layer 35positive buffer layer 37 positive active material layer

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. As those skilled in the art would realize, thedescribed embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the present invention.

Parts that are irrelevant to the description will be omitted to clearlydescribe the present disclosure, and like reference numerals designatelike elements throughout the specification.

FIG. 1 illustrates a schematic view showing a cross-sectional structureof an all solid state battery according to an embodiment of the presentinvention, FIG. 2 schematically illustrates a cross-sectional structureof a negative electrode of an all solid state battery according to anembodiment of the present invention, and FIG. 3 schematicallyillustrates a cross-sectional structure of a positive electrode of anall solid state battery according to an embodiment of the presentinvention.

Referring to FIG. 1 , the all solid state battery 1 according to theembodiment of the present invention includes a sulfide-based solidelectrolyte layer 10, a negative electrode 20, and a positive electrode30.

The negative electrode 20 is stacked on a first surface of the solidelectrolyte layer 10, and the positive electrode 30 is stacked on asecond surface thereof.

For example, based on the solid electrolyte layer 10, the negativeelectrode 20 may be stacked at a lower side, and the positive electrode30 may be stacked at an upper side.

In an embodiment of the present invention, the left and right, front andrear, and up and down directions are set based on the drawing, and aportion facing an upper side is defined as an upper portion, an upperend, an upper surface, and an upper side portion, and a portion facing alower side will be defined as a lower portion, a lower end, a lowersurface, and a lower end portion.

The definition of the reference direction as described above is arelative meaning, and the direction may vary depending on the referenceposition of the all solid state battery 1 of embodiments of the presentinvention, and the reference direction described above is notnecessarily limited to the reference direction of the presentembodiment.

In an embodiment of the present invention, the solid electrolyte layer10 may be formed of a sulfide-based material including a lithiumsulfide-based compound or an argyrodite-based compound.

This has an advantage that the sulfide-based material applied to thesolid electrolyte layer 10 has a superior soft characteristic comparedto an oxide-based material, and is suitable for a structuralcharacteristic of the all solid state battery 1 according to theembodiment of the present invention.

A material having ionic conductivity of 1*10⁻³ S/cm or more may be usedfor the solid electrolyte layer 10.

In addition, the solid electrolyte layer 10 may have a particle size(average diameter of each grain constituting the powder) in a range of0.1 µm or more and 10 µm or less.

The solid electrolyte layer 10 may have a density that is set in a rangeof 0.1 g/cm³ or more and 1 g/cm³ or less.

The solid electrolyte layer 10 may be formed to have a thickness of 50µm or more and 100 µm or less.

Referring to FIG. 2 , in an embodiment of the present invention, thenegative electrode 20 includes a negative current collector 21, anegative primer layer 23, a negative buffer layer 25, and a negativeactive material layer 27.

The negative current collector 21 may include at least one of copper,stainless steel, titanium, iron, and nickel.

The negative current collector 21 has surface roughness formed on anupper surface thereof.

The surface roughness refers to a degree of fine irregularitiesgenerated on the surface.

Such surface roughness may be formed through plasma surface treatment orcorona surface treatment.

The negative current collector 21 may have a thickness of 15 µm or moreand 20 µm or less.

In addition, the negative primer layer 23 is formed on an upper surfaceof the negative current collector 21.

The negative primer layer 23 may be formed of a mixture of acarbon-based conductive material and a binder.

For example, the negative primer layer 23 can be formed by mixing aconductive material and a binder at a ratio of 7:3 to 9.5:0.5.

The negative primer layer 23 may be formed to have a thickness of 1 µmor less.

The negative buffer layer 25 is formed on an upper surface of thenegative primer layer 23.

The negative buffer layer 25 may be formed by mixing a sulfide-basedmaterial, a conductive material, and a binder.

For example, the negative buffer layer 25 may be formed of a mixture ofa sulfide-based material that is set in a range of 60 wt% or more and 90wt% or less, a conductive material that is set in the range of 9 wt% ormore and 30 wt% or less, and a binder that is set in a range of 1 wt% ormore and 10 wt% or less, based on 100 wt% of a total weight.

The negative buffer layer 25 may have the same ionic conductivity andelectronic conductivity as those of the negative active material layer27.

For example, the negative buffer layer 25 may have ionic conductivitythat is set in a range of 1 mS/cm or more and 9.99*10⁻⁹ S/cm or less.

In addition, the negative buffer layer 25 has softness that is higherthan that of the negative primer layer 23.

The negative buffer layer 25 may be formed to have a thickness of 20 µmor more and 100 µm or less.

The negative active material layer 27 is formed on an upper surface ofthe negative buffer layer 25.

The negative active material layer 27 may be formed of a mixture of asulfide-based material, a negative active material, a conductivematerial, and a binder.

For example, the negative active material layer 27 may be formed of amixture of a sulfide-based material in a range of 8 wt% to 30 wt%, anegative active material in a range of 60 wt% to 90 wt%, a conductivematerial in a range of 1 wt% to 10 wt%, and a binder in a range of 1 wt%to 10 wt%, based on 100 wt% of a total weight.

The negative active material layer 27 may be formed to have a thicknessof 20 µm or more and 100 µm or less.

The solid electrolyte layer 10 is disposed on an upper surface of thenegative active material layer 27.

In addition, the positive electrode 30 is formed on an upper surface ofthe solid electrolyte layer 10, and is formed to be symmetrical with thenegative electrode 20 with respect to the solid electrolyte layer 10.

Referring to FIG. 3 , the positive electrode 30 is formed in the samemanner as the negative electrode 20, and then is inverted in a verticaldirection to be stacked on an upper surface of the solid electrolytelayer 10, but a structure will be described based on a direction shownin FIG. 1 .

Accordingly, the positive electrode 30 will be described starting withthe positive current collector 31 positioned at an outermost upperportion thereof.

In the present embodiment, the positive electrode 30 includes thepositive current collector 31, a positive primer layer 33, a positivebuffer layer 35, and a positive active material layer 37.

The positive current collector 31 may include at least one of stainlesssteel, titanium, iron, nickel, aluminum, and chromium.

The positive current collector 31 has surface roughness formed on alower surface thereof.

The surface roughness on the positive current collector 31 is the sameas the surface roughness on the negative current collector 21.

The positive current collector 31 may have a thickness of 15 µm or moreand 20 µm or less.

In addition, the positive primer layer 33 is formed on a lower surfaceof the positive current collector 31.

The positive primer layer 33 may be formed of a mixture of acarbon-based conductive material and a binder.

For example, the positive primer layer 33 can be formed by mixing aconductive material and a binder at a ratio of 7:3 to 9.5:0.5.

The positive primer layer 33 may be formed to have a thickness of 1 µmor less.

The positive buffer layer 35 is formed on a lower surface of thepositive primer layer 33.

The positive buffer layer 35 may be formed by mixing a sulfide-basedmaterial, a conductive material, and a binder.

For example, the positive buffer layer 35 may be formed of a mixture ofa sulfide-based material that is set in a range of 60 wt% or more and 90wt% or less, a conductive material that is set in the range of 9 wt% ormore and 30 wt% or less, and a binder that is set in a range of 1 wt% ormore and 10 wt% or less, based on 100 wt% of a total weight.

The positive buffer layer 35 may have the same ionic conductivity andelectronic conductivity as those of the positive active material layer37.

For example, the positive buffer layer 35 may have ionic conductivitythat is set in a range of 1 mS/cm or more and 9.99*10⁻⁹ S/cm or less.

In addition, the positive buffer layer 35 has softness that is higherthan that of the positive primer layer 33.

The positive buffer layer 35 may be formed to have a thickness of 1 µmor more and 5 µm or less.

The positive active material layer 37 is formed on a lower surface ofthe positive buffer layer 35.

The positive active material layer 37 may be formed of a mixture of asulfide-based material, a positive active material, a conductivematerial, and a binder.

For example, the positive active material layer 37 may be formed of amixture of a sulfide-based material in a range of 8 wt% to 30 wt%, apositive active material in a range of 60 wt% to 90 wt%, a conductivematerial in a range of 1 wt% to 10 wt%, and a binder in a range of 1 wt%to 10 wt%, based on 100 wt% of a total weight.

The positive active material layer 37 may be formed to have a thicknessof 20 µm or more and 100 µm or less.

The solid electrolyte layer 10 is disposed on a lower surface of thepositive active material layer 37.

A manufacturing method of the all solid state battery configured asdescribed above will be as follows.

FIG. 4 to FIG. 11 illustrate views sequentially showing a manufacturingmethod of an all solid state battery according to an embodiment of thepresent invention.

In accordance with the manufacturing method of the all solid statebattery, the negative electrode 20 and the positive electrode 30 areseparately manufactured, and then the negative electrode 20 and thepositive electrode 30 are bonded to a first side and a second side ofthe solid electrolyte layer 10, respectively.

In this case, the negative electrode 20 is disposed on a lower surfaceof the solid electrolyte layer 10, and the positive electrode 30 isdisposed on an upper surface of the solid electrolyte layer 10.

Accordingly, the positive electrode 30 may be formed to be symmetricalwith the negative electrode 20 with respect to the solid electrolytelayer 10 by stacking each material in order, and then by inverting it ina vertical direction and bonding it to the upper surface of the solidelectrolyte layer 10.

Referring to FIG. 4 , surface roughness is formed on an upper surface ofthe negative current collector 21 through a surface treatment.

The surface treatment may include a plasma surface treatment or a coronasurface treatment.

The plasma surface treatment or corona surface treatment is a process ofroughening a surface by irradiating plasma or corona on the uppersurface of the negative current collector 21 to change a state of thesurface.

This surface treatment is to increase a bonding area depending on thesurface roughness.

Referring to FIG. 5 , the negative primer layer 23 is formed on theupper surface of the negative current collector 21.

The negative primer layer 23 is formed through wet coating, and the wetcoating may include gravure coating and slot die coating, for example.

The negative primer layer 23 may prevent corrosion of the negativecurrent collector 21.

In addition, the negative primer layer 23 is made of a mixture of acarbon-based conductive material and a binder, and electronicconductivity may be improved by the carbon-based conductive material.

Referring to FIG. 6 , the negative buffer layer 25 is formed on an uppersurface of the negative primer layer 23.

The negative buffer layer 25 is formed through wet coating, and the wetcoating may include gravure coating and slot die coating, for example.

The negative buffer layer 25 has softness that is higher than that ofthe negative primer layer 23.

The negative buffer layer 25 may move ions and electrons, therebyimproving capacitance.

Referring to FIG. 7 , the negative active material layer 27 is formed onan upper surface of the negative buffer layer 25.

The negative active material layer 27 may have the same ionicconductivity and electronic conductivity as those of the negative bufferlayer 25.

Referring to FIG. 8 , when the negative current collector 21, thenegative primer layer 23, the negative buffer layer 25, and the negativeactive material layer 27 are stacked as described above, a rollingprocess is performed.

In this case, the rolling process is performed at a pressure that is setin a range of 0.1 MPa or more and 10 MPa or less.

The negative electrode 20 increases physical cohesion between thenegative buffer layer 25 and the negative active material layer 27during the rolling process due to high softness of the negative bufferlayer 25.

Referring to FIG. 9 , the solid electrolyte layer 10 is formed on anupper surface of the negative active material.

The solid electrolyte layer 10 is formed through wet coating, and thewet coating may include gravure coating and slot die coating, forexample.

Ions may move through the solid electrolyte layer 10.

Next, steps of FIG. 4 to FIG. 8 are repeated to form the positiveelectrode 30.

That is, surface roughness is formed on an upper surface of the positivecurrent collector 31 through a surface treatment, the positive primerlayer 33 is formed on the upper surface of the positive currentcollector 31, the positive buffer layer 35 is formed on an upper surfaceof the positive primer layer 33, and the positive active material layer37 is formed on an upper surface of the positive buffer layer 35.

Referring to FIG. 10 , the positive electrode 30 formed as describedabove is inverted in the vertical direction, and then is stacked on theupper surface of the solid electrolyte layer 10.

In other words, the positive active material layer 37 of the positiveelectrode 30 is disposed to contact the solid electrolyte layer 10, andis stacked.

Referring to FIG. 11 , a rolling process is performed on the negativeelectrode 20, the solid electrolyte layer 10, and the positive electrode30 which are stacked.

In this case, the rolling process is performed at a pressure that is setin a range of 0.1 MPa or more and 10 MPa or less.

The all solid state battery 1 may improve binding strength between thenegative active material, the solid electrolyte layer 10, and thepositive active material through the rolling process.

Accordingly, in accordance with the all solid state battery and amanufacturing method thereof according to the embodiments of the presentinvention, it is possible to minimize electrode porosity that may occurafter a rolling process by applying a negative electrode buffer layerand a positive electrode buffer layer, and maximizing interlayerinterfacial adhesion areas.

Thus, in accordance with the all solid state battery and a manufacturingmethod thereof, ions and electrons may move uniformly at upper and lowerportions of an electrode, thereby improving the output and durability.

In addition, in accordance with the all solid state battery and amanufacturing method thereof according to the embodiments of the presentinvention, it is possible to minimize deformation caused by volumechange of the negative active material or positive active material thatmay occur during charging and discharging, resultantly improving a lifecharacteristic.

While the present invention has been particularly shown and describedwith reference to specific embodiments thereof, it will be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the following claims.

What is claimed is:
 1. A method of manufacturing an all solid statebattery, the method comprising: forming a negative electrode including anegative active material layer and a negative buffer layer; forming asulfide-based solid electrolyte layer on a first surface of the negativeelectrode; forming a positive electrode including a positive activematerial layer and a positive buffer layer; and bonding the positiveelectrode to a second surface of the solid electrolyte layer.
 2. Themethod of claim 1, wherein forming the negative electrode comprises:forming surface roughness on a first surface of a negative currentcollector through a surface treatment; forming a negative primer layeron the first surface of the negative current collector through wetcoating; forming the negative buffer layer having higher softness thanthat of the negative primer layer on a first surface of the negativeprimer layer through wet coating; forming the negative active materiallayer having a same ionic conductivity and electronic conductivity asthe negative buffer layer on a first surface of the negative bufferlayer; and rolling the negative current collector, the negative primerlayer, the negative buffer layer, and the negative active material layerwhich are stacked.
 3. The method of claim 2, wherein the sulfide-basedsolid electrolyte layer is formed on a first surface of the negativeactive material layer through wet coating.
 4. The method of claim 2,wherein the negative primer layer comprises a mixture of a carbon-basedconductive material and a first binder.
 5. The method of claim 2,wherein the negative buffer layer comprises a mixture of a firstsulfide-based material, a first conductive material, and a secondbinder, wherein the negative buffer layer has a different compositionthan the negative active material layer.
 6. The method of claim 2,wherein the negative buffer layer has a degree of softness that ishigher than that of the negative primer layer.
 7. The method of claim 2,wherein the negative active material layer comprises a mixture of asecond sulfide-based material, a negative electrode active material, asecond conductive material, and a third binder, and wherein the negativeactive material layer is in contact with the solid electrolyte layer. 8.The method of claim 1, wherein forming the positive electrode comprises:forming surface roughness on a first surface of a positive currentcollector through a surface treatment; forming a positive primer layercomprising a mixture of a carbon-based material and a first binder on afirst surface of the positive current collector through wet coating;forming the positive buffer layer having higher softness than thepositive primer layer on a first surface of the positive primer layer;forming the positive active material layer having a same ionicconductivity and electronic conductivity as the positive buffer layer ona first surface of the positive buffer layer; and rolling the positivecurrent collector, the positive primer layer, the positive buffer layer,and the positive active material layer which are stacked.
 9. The methodof claim 8, wherein the positive buffer layer comprising a mixture of afirst sulfide-based material, a first conductive material, and a secondbinder without an active material, wherein the positive buffer layer hasa different composition than the positive active material layer.
 10. Themethod of claim 8, wherein the positive buffer layer has a degree ofsoftness that is higher than that of the positive primer layer.
 11. Themethod of claim 1, wherein bonding the positive electrode includes:inverting the positive electrode in a vertical direction and contactingthe sulfide-based solid electrolyte layer with the positive activematerial layer of the positive electrode; and rolling the negativeelectrode, the sulfide-based solid electrolyte layer, and the positiveelectrode.
 12. A method of forming all solid state battery, the methodcomprising: forming a negative active material layer on a first surfaceof a solid electrolyte layer; forming a negative buffer layer on a firstsurface of the negative active material layer, the negative buffer layercomprising a mixture of a first sulfide-based material, a firstconductive material, and a second binder, wherein the negative bufferlayer has a different composition than the negative active materiallayer; forming a negative primer layer on a first surface of thenegative buffer layer, wherein the negative buffer layer has a degree ofsoftness that is higher than that of the negative primer layer; andforming a negative current collector layer having a second surfacedisposed on a first surface of the negative primer layer, the secondsurface of the negative current collector layer having a surfaceroughness; and forming a positive active material layer on a secondsurface of the solid electrolyte layer; forming a positive buffer layeron a second surface of the positive active material layer the positivebuffer layer comprising a mixture of the first sulfide-based material,the first conductive material, and the second binder without an activematerial, wherein the positive buffer layer has a different compositionthan the positive active material layer; forming a positive primer layeron a second surface of the positive buffer layer, wherein the positivebuffer layer has a degree of softness that is higher than that of thepositive primer layer; and forming a positive current collector layerhaving a first surface disposed on a second surface of the positiveprimer layer, the first surface of the positive current collector layerhaving a surface roughness.
 13. The method of claim 12, wherein thenegative primer layer comprises a mixture of a carbon-based conductivematerial and a first binder, and wherein the negative active materiallayer comprises a mixture of a second sulfide-based material, a negativeelectrode active material, a second conductive material, and a thirdbinder, wherein the negative active material layer is in contact withthe solid electrolyte layer.
 14. The method of claim 13, wherein themixture of the carbon-based conductive material and the first binder ofthe negative primer layer has a ratio of 7:3 to 9.5:0.5.
 15. The methodof claim 12, wherein the mixture of the negative buffer layer comprisesthe first sulfide-based material in a range of 60 wt% or more and 90 wt%or less, the first conductive material in a range of 9 wt% or more and30 wt% or less, and the second binder in a range of 1 wt% or more and 10wt% or less, based on 100 wt% of a total weight.
 16. The method of claim12, wherein the negative buffer layer has a same ionic conductivity andelectronic conductivity as the negative active material layer.
 17. Themethod of claim 12, wherein the positive primer layer comprises amixture of a carbon-based conductive material and a first binder, andwherein the positive active material layer comprises a mixture of asecond sulfide-based material, a positive electrode active material, asecond conductive material, and a third binder, wherein the positiveactive material layer is in contact with the solid electrolyte layer.18. The method of claim 17, wherein the mixture of the carbon-basedconductive material and the first binder of the positive primer layerhas a ratio of 7:3 to 9.5:0.5.
 19. The method of claim 12, wherein themixture of the positive buffer layer comprises the first sulfide-basedmaterial in a range of 60 wt% or more and 90 wt% or less, the firstconductive material in a range of 9 wt% or more and 30 wt% or less, andthe second binder in a range of 1 wt% or more and 10 wt% or less, basedon 100 wt% of a total weight.
 20. The method of claim 12, wherein thepositive buffer layer has a same ionic conductivity and electronicconductivity as the positive active material layer.